FIG. 6 is a schematic configuration view of a water heater including a downward combustion type-flat burner (3a) disposed on a lower surface of a burner body (40) in such a manner that a combustion surface (30a) is disposed facedown. In the water heater, the burner body (40) is provided in an upper region of the casing (4).
Additionally, a sensible heat recovery type-primary heat exchanger (311) is disposed below the combustion surface (30a) of the flat burner (3a), and a latent heat recovery type-secondary heat exchanger (321) is disposed below the sensible heat recovery type-primary heat exchanger (311).
In such a water heater, all air taken in by rotating a fan (not shown) in a fan case (41) is fed as primary combustion air to the flat burner (3a) in such a manner that the combustion surface (30a) is disposed facedown in the burner body (40). Moreover, fuel gas is supplied from a gas supply pipe (44) to a plurality of gas nozzles (42) provided above the flat burner (3a). The fuel gas is mixed with the above-described primary combustion air, and then is fed to the flat burner (3a).
In the above-described water heater, in order to minimize the height of the upper region of the casing (4), the fan case is laid on its side so as not to be in a vertical standing posture, so that a blowout port (45) which opens to one side of the fan case (41) is communicated with an inlet port (310) which opens to one side surface of the burner body (40), as illustrated in FIG. 6. In this configuration, the burner body (40) and the fan case (41) are aligned in a left-and-right direction, which results in reducing the overall height of the casing (4).
However, in such a conventional installation structure of the fan case (41) shown in FIG. 6, the fan inside the fan case (41) is also installed in a state laid on its side. Therefore, when a diameter of the fan becomes large, a diameter of the fan case (41) also becomes large. As a result, as illustrated in FIG. 6, there is a problem that an installation of the fan case (41) on a lateral side of the burner body (40) increases a width in the left-and-right direction of the casing (4). Moreover, there is a problem that when the fan case (41) is installed in front of, or in rear of the burner body (40), a depth of the casing (4) increases.